There are some differences between CPDLC that is used in oceanic airspace and other regions of the world as part of FANS 1/A and the ATN-B1 type of CPDLC being implemented in Europe, which the Europeans have branded Link 2000+.
It is possible for an airplane to be equipped with only FANS 1/A, or ATN-B1, or both; therefore, an airplane that is capable of using CPDLC over the North Atlantic may not be capable of CPDLC throughout Europe, and airplanes that are CPDLC capable in Europe may not be capable over the North Atlantic or in many other areas of the world.
There are also some differences in uplink/downlink messages between the two systems. This is why training on region-specific CPDLC differences is important.
Some airplanes are capable of an automatic transition from a FANS 1/A sector to an ATN-B1 sector and vice versa. In some airplanes, the crew must manually log on to the new next ATSU when transitioning from FANS 1/A service to ATN-B1 or vice-versa.
Due to frequent "provider aborts" that Maastricht Upper Area Control Centre (MUAC) was experiencing with certain avionics packages, they have instituted a white list to ensure that only approved aircraft with avionics packages that have proven to perform well, or with packages that they have insufficient data on, are allowed to access their ATN-B1 services. Operators must apply to have their aircraft added to this list before their aircraft's ATN-B1 request will be accepted by MUAC. Click here for more information